Marvair Scholar III™ VAISA I&S Manual 03/2019 Rev. 8
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operation. No light indicates an open switch. See lockout indicator “A” under
Outputs.
•
LPS
– Low Refrigerant Pressure Switch. The LPS is ON during normal operation.
No light indicates an open switch. See lockout indicator “A” under Outputs
•
HUM
– Humidity Controller. Used when an external humidity controller operates
the Scholar to control the humidity in the classroom.
•
EHDD
– Electric Heat During Defrost. Allows the user to select whether electric
heat operates when the heat pump enters into the defrost mode. The units are
wired at the factory to prevent the electric heaters from operating during the
defrost mode. For operation during defrost, a wire is moved from one terminal to
another in the control box. NOTE: for operation of the electric heat during defrost,
the electric heat control must be configured to allow simultaneous operation of
the electric heat and the compressor. (heat pump only)
•
SCKT
– “S” Circuit. Signal that indicates the electric heat and the compressor
can never operate simultaneously. This function is controlled by the electric heat
control toggle switch in the control center. The LED should be ON if “Y” is ON,
the electric heat is on and the toggle switch is in the S circuit position. (heat pump
only)
•
ODS
– Outdoor Thermostat. Determines at what outdoor temperature (factory set
at 40°F), the supplemental heat turns on. The LED should be ON if the outdoor
temperature is below the ODS set point. (heat pump only)
•
EMS
– Energy Management System. A shutdown input from an external source.
•
GWR
– GreenWheel
®
ERV Relay. When this LED is lit, the GreenWheel ERV is
operating.
•
DFC
– Defrost Control Thermostat. Indicates whether the defrost thermostat is
closed. The defrost cycle is based upon both time (see defrost timer) and outdoor
coil temperature. (heat pump only)
PLC Outputs
An output is a signal from the PLC to the Scholar III™ heat pump or air conditioner
